X-ray tubes are for example used in CT systems wherein the X-ray tube is rotating about a patient, generating a fan-beam of X-rays, wherein opposite to the X-ray tube and with it on a gantry rotor rotates a detector system which converts the detected X-rays into electrical signals. Based on these electrical signals, a computer system may reconstruct an image of the patient's body.
In the X-ray tube, a beam of primary electrons emitted from a cathode hits a focal spot of a target and creates X-rays. Therein, a major part of incident electron energy is converted into heat.
Current high-power X-ray tubes might often operate at their material related limits. Especially the target may be constantly under the risk of damaging caused by excessive heat.
In order to prevent damaging of the target and the X-ray tube in general, it may be beneficial to constantly monitor the temperature of the target. Such monitoring will aid in the protection of the patient, the radiologist and the imaging apparatus.
Some conventional tube designs are adapted to measure the temperature of the target by means of e.g. thermal radiation detectors or infra-red light detectors.
However, such measurement techniques may be complex in construction and expensive. Moreover, it may be difficult to get a robust signal, especially in an electrically noisy environment, or when the quality of optical elements like glass windows deteriorate due to vapor deposition in the course of the tube life.